JP2539461B2 - Straightness meter - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a straightness meter of a system in which a displacement detector is moved in a direction orthogonal to its measuring direction to measure the straightness of an object to be measured. It is a thing.

[Conventional technology]

As a method for measuring the straightness of the straight line part of the object, various methods are used depending on the size and shape of the object to be measured and the required measurement accuracy, but in general, a straight ruler, which is the standard of measurement, is used. Then, the distance between each point of the straight line portion to be measured of the object to be measured with respect to the straight edge is measured, and the straightness is obtained from the difference in the distance between these points.

Conventionally, as a straightness meter for determining straightness by the above method, for example, a rectangular cross-section straight ruler having a narrow reference plane that serves as a reference for straightness measurement, and a movable table slidably provided on this reference plane. There is known a straightness meter having a configuration in which a displacement detector is fixed to the moving table so that its measuring direction is perpendicular to the reference plane.

In order to obtain the straightness using the straightness meter having the above configuration, first, the reference surface of the straight ruler is parallel to the plane including the straight line portion to be measured of the object to be measured, and the moving direction of the moving table is Install the straightness meter so that it matches the straight line part to be measured.

Next, the movable table is moved until the measurement piece of the displacement detector coincides with the measurement start point of the straight line portion to be measured, and the detected amount of the displacement detector at this time is recorded. Then, the movable table is moved so that the measuring piece traces the linear portion of the object to be measured, and the detected amount of the displacement detector is sequentially recorded until the measuring piece reaches the measurement end point.

If the difference between the maximum value and the minimum value of the amount of detection from the measurement start point to the measurement end point obtained in this way is calculated, that value becomes the calculated straightness.

[Problems to be solved by the invention]

However, in the straightness meter having the above-mentioned configuration, since the moving table is configured to slide on the reference surface, there are drawbacks as described below.

When the moving table is slid on the reference surface, variations in sliding resistance due to shape errors of the sliding surface of the moving table or the reference surface of the straightedge, or changes in surface conditions such as oil film on the reference surface, Due to the reaction force measured by the displacement detector and the elastic deformation of the movable table and the straight ruler due to the weight of the movable table, the movable table slides on the reference surface while meandering irregularly. For this reason, the measurement piece of the displacement detector fixed to the moving table cannot accurately trace the linear portion of the measurement target, and the displacement detector includes an irregular movement error. Will end up.

To reduce this movement error, it is necessary to improve the accuracy of the sliding surface of the moving table and the reference surface of the straight edge, use precision linear motion bearings, or increase the rigidity of the moving table and the straight edge. However, even if these means are used, they cannot be a solution to the movement error.

In other words, if the accuracy of the sliding surface of the moving table or the straight-liner reference surface is improved, or if the accuracy of the linear motion bearing used is improved, the cost required for this will increase significantly, and the cost of the straightness meter as a whole will be increased. It will be a factor to increase. Therefore, in order to manufacture a straightness meter within an appropriate cost range, there is no choice but to allow some error.

Also, increasing the rigidity of the moving table and the straight edge ruler will increase the size of the moving table and the straight edge ruler, and may increase the weight.Therefore, it is necessary to increase the rigidity of other parts of the straightness meter accordingly. However, as the rigidity is increased, the size of the straightness meter is infinitely increased. Therefore, the rigidity of the movable table and the straight edge, which can be obtained within the range of the size suitable for the effective measurement range of the straightness meter, is naturally limited.

In the present invention, in view of the above circumstances, the accuracy of the component parts is kept the same as the conventional one, and the size thereof is limited to the minimum increase, and the straightness is less affected by the movement error caused by the movement of the moving table. The purpose is to provide a meter.

[Means for solving problems]

The straightness meter of the present invention is capable of moving on a reference gauge having a flat reference straight portion, a guide rail having a longitudinal direction in a direction parallel to the reference straight portion, and a guide rail parallel to the reference straight portion. A movable table provided on the movable table, a first displacement detector that is fixed to the movable table and detects a displacement of a linear portion of the object to be measured with respect to the movable table, and a movable table that is fixed to the movable table with respect to the reference straight portion. A second displacement detector that detects displacement, and a displacement of the linear portion of the measured object with respect to the reference straight portion by correcting the detection amount of the first displacement detector based on the detection amount of the second displacement detector. And an arithmetic unit for calculating

[Action]

The following procedure is used to obtain the straightness using the straightness meter having the above configuration.

First, in the straightness meter of this configuration, since the two displacement detectors are fixed to one moving base, the amount of detection of each displacement detector when the moving base causes an error with respect to linear motion Has a specific correlation depending on the shape of the moving table and the mounting position of each displacement detector. Therefore, the correlation is clarified before the straightness is measured, and the correction value of the detection amount of the first displacement detector with respect to the detection amount of the second displacement detector is determined.

Next, the straightness meter is set such that the reference straight portion of the reference gauge is parallel to the plane including the straight line portion to be measured of the object to be measured, and the moving direction of the movable table matches the straight line portion to be measured. To install. Then, the first displacement detector moves the movable table to a position where the displacement of the measurement start point of the linear portion of the measurement target can be detected, and the detection amount of the first displacement detector at this time is recorded, and at the same time the second displacement detector is recorded. Record the amount detected by the displacement detector. Then, the movable table is moved so that the first displacement detector can sequentially detect the displacement of each point of the straight line portion of the measurement object, and the detection amount of each displacement detector is sequentially recorded. Then, when the first displacement detector detects the displacement at the measurement end point of the linear portion to be measured, the measurement ends.

During the above measurement, the second displacement detector detects each point of the reference straight portion, so if the movable table makes a linear movement in parallel to the reference straight portion, the detected amount is always constant. Must. Therefore, if the detection amount of the second displacement detector fluctuates from the value at the measurement start position, this fluctuation value is considered to be a value generated because the movable table meandered.
Therefore, if this displacement value is corrected by the previously calculated correction value and converted into the detection amount of the first displacement detector, the displacement of the moving table included in the detection amount recorded by the first displacement detector is converted. Movement error is required. Therefore, the above-mentioned correction value is added to the fluctuation value of the detection amount of the second displacement detector at each position of the moving table by the arithmetic unit to convert it to the amount equivalent to the detection amount of the first displacement detector, and these conversion values are converted. By subtracting from the detection amount of the first displacement detector at each position of the movable table, the true detection amount of the first displacement detector that does not include the movement error can be obtained. Then, a reference line is mathematically provided from the true detection amount of the first displacement detector thus obtained, and if the maximum value of the difference between this reference line and the true detection amount is obtained, the straight line portion to be measured is obtained. The exact straightness of is required.

〔Example〕

1 to 4 show one embodiment of the straightness meter of the present invention.

Reference numeral 1 in the drawing is a reference gauge for a measurement reference, which is a prism having a rectangular cross section as shown in FIG. 4, and a flat reference surface 1a including a straight portion serving as a measurement reference on a lower narrow surface thereof.
Are formed. Diagonally below the reference gauge 1,
As shown in FIGS. 2 to 4, a guide rail 2 having the same shape and size as the reference gauge 1 is provided. The reference gauge 1 and the guide rail 2 are respectively provided as shown in FIGS. 2 and 3. Both ends are fitted in the fixed blocks 3a, 3b and fixed in parallel with each other.

In addition, reference numeral 4 in the drawing is a mobile table. As shown in FIG. 4, a rectangular hole 4a slightly larger than the cross-sectional dimension of the guide rail 2 is formed in the vicinity of the center of the moving table 4, and the rectangular hole 4a and the guide rail 2 are fitted to each other to move the rectangular rail 4a. The table 4 is slidable along the guide rail 2 in the longitudinal direction of the reference surface 1a of the reference gauge 1.

In the vicinity of the reference surface 1a of the movable table 4, as shown in FIG. 4, a flat surface portion 4b orthogonal to the reference surface 1a and parallel to the longitudinal direction of the reference surface 1a is formed. The flat portion 4b has a first
As shown in the figure, two lever type displacement detectors 5 and 6 are fixed in parallel in a direction orthogonal to the reference plane 1a, and each measurement direction is orthogonal to the reference plane 1a. There is. The measuring piece 5a of the lever type displacement detector 5 is oriented so that it can come into contact with the surface facing the reference surface 1a with the displacement detectors 5 and 6 interposed therebetween. The measuring piece 6a of the container 6 is brought into contact with the reference straight portion of the reference surface 1a. These displacement detectors 5 and 6 have respective measuring pieces 5a,
This is for measuring minute displacements of 6a in the measuring direction, converting these into electric signals, and then inputting them into an arithmetic unit described later to record the displacements of the measuring pieces 5a, 6a. Further, the moving table 4 has an adjusting screw for finely adjusting the inclination of the lever type displacement detector 5.
4c is provided.

On the other hand, as shown in FIGS. 1 and 2, a motor 7 for linearly moving the moving table 4 is fixed to the side surface of the fixed block 3a with its rotation shaft 7a orthogonal to the reference plane 1a. A drive pulley 8 is fixed to the tip of the rotary shaft 7a. Further, as shown in FIGS. 1 to 3, a driven pulley 9 is provided on the outer side surfaces of the fixed blocks 3a and 3b.
The respective rotating surfaces are rotatably arranged such that they are flush with the rotating surface of the drive pulley 8, and the drive pulley 8 and the driven pulley 9 have the fixed blocks 3a, 3b and the movable table 4 respectively. A steel wire 10 is wound through the wire. The steel wire 10 is wound with an appropriate tension so that it does not expand or contract due to the torque fluctuation of the motor 7. The steel wire 10 is integrally connected to the moving table 4 by pressing the penetrating portion of the moving table 4 with the set screw 4d, so that the rotational movement of the motor 7 is converted into the linear movement of the moving table 4 as described above. To be converted.

Further, support legs 11 and 12 having conical tips are provided on the lower surfaces of the fixed blocks 3a and 3b to support the straightness meter. The tips of the supporting legs 11 and 12 are slightly higher than the free position of the measuring piece 5a of the lever type displacement detector 5, and the supporting legs are on a plane including the linear portion 14 of the object to be measured.
When 11 and 12 are brought into contact, the measuring piece 5a is
It can be brought into contact with. The upper portion of the support leg 12 is connected to the adjusting screw 13, and the supporting leg 12 can be moved up and down by turning the adjusting screw 13. This is because the inclination of the straightness meter is set so that the reference surface 1a of the reference gauge 1 and the straight portion 14 are exactly parallel when the straightness meter is installed on a plane including the linear portion 14 to be measured. It is for adjustment.

In order to obtain the straightness using the straightness meter having the above structure, the following procedure is performed.

First, install the straightness meter on the flat surface of the object to be measured, and move the moving table 4
Movement of the lever causes the measuring piece 5a of the lever type displacement detector 5 to move straight
Adjust the position of the straightness meter so that you can trace 14. Then, the parallelism between the reference surface 1a of the reference gauge 1 of the straightness meter and the linear portion 14 is adjusted by the adjusting screw 13.

Next, the motor 7 is started, the measurement piece 5a is made to coincide with the measurement start point of the linear portion 14, and the measurement is started. Then, by rotating the motor 7 at a constant speed to move the moving table 4 toward the measurement end point at a constant speed, the measuring piece 5a is on the straight line portion 14 and the measuring piece 6a is the reference straight portion of the reference surface 1a. The upper part is traced at a constant speed, and the measurement ends when the measurement piece 5a reaches the measurement end point.

During the above measurement, the displacement detectors 5 and 6 are connected to a computing unit (not shown), and the amount of detection is sequentially processed. From the computing unit, the displacement of the measuring piece 5a of the displacement detector 5 in the measuring direction is determined based on the displacement table 4. An accurate displacement amount is output by removing the movement error of.

That is, since the movable table 4 moves linearly in parallel with the reference plane 1a, the detection amount detected by the lever type displacement detector 6 should always show a constant value from the start to the end of measurement. Therefore, if the detection amount of the lever type displacement detector 6 fluctuates from the value at the measurement start point, this fluctuation value is generated because the moving table 4 meanders in the measuring direction of the displacement detectors 5 and 6. Considered to be a value. On the other hand, since the lever type displacement detectors 5 and 6 are attached so as to be integrated with the movable table 4, the fluctuation values detected by the displacement detectors 5 and 6 when the movable table 4 makes a meandering motion are There is a certain correlation. Therefore, by clarifying this correlation, a correction value for converting the fluctuation value of the detection amount of the lever type displacement detector 6 into the fluctuation value of the lever type displacement detector 5 is determined, and the fluctuation of the lever type displacement detector 6 is determined. Correct the value with this correction value to convert it into the fluctuation value of the lever type displacement detector 5, and subtract this converted value from the detected amount of the lever type displacement detector 5 to obtain the accurate amount of detection of the lever type displacement detector 5. Will be obtained.

Therefore, the arithmetic unit sequentially obtains the variation value of the detection amount of the lever type displacement detector 6 from the detection amount at the measurement start point,
This fluctuation value is corrected by the above-mentioned correction value and converted into the amount corresponding to the detected amount of the first displacement detector, and the converted value is subtracted from the detected amount of the lever type displacement detector 5, and this subtracted value is subtracted. If a value is output and continuously recorded by a recorder, an accurate shape curve of the linear portion 14 that does not include the movement error of the moving table 4 is obtained, and a mathematical reference line is provided on this curve.
The maximum value of the difference between the reference line and the curve is the calculated straightness.

As described above, in the straightness meter of this embodiment,
Since the lever-type displacement detector 6 having the measuring piece 6a to be brought into contact with the reference surface 1a is fixed to the movable table 4 together with the lever-type displacement detector 5, the movement error of the movable table 4 can be detected, and the movement error can be dealt with. Then, the detection amount of the lever type displacement detector 5 can be corrected. Therefore, the reference surface 1a of the reference gauge 1 has the same accuracy as the reference surface of the conventional straight edge ruler, and the shape error of the guide rail 2 and the rectangular hole 4a of the movable table 4 does not cause any problem. The size of the guide rail 2 and the lever type displacement detector 6 can be increased, and the size is sufficiently appropriate in view of the effective measurement range of the straightness meter. Further, since the moving table 4 is supported by the guide rails 2, the reference gauge 1 is not loaded with its own weight, and thus the moving table 4 is
The reference gauge 1 cannot be elastically deformed due to the movement of the reference gauge, and it is possible to use a reference gauge having a smaller rigidity, that is, a smaller cross-sectional dimension than that of the conventional straight ruler. The increase can be further reduced.
Further, in the present embodiment, the reference surface 1a of the reference gauge 1 is opposed to the plane of the object to be measured, and the two lever type displacement detectors 5 and 6 are arranged side by side in the direction orthogonal to the reference surface 1a. The reaction forces measured by the displacement detectors 5 and 6 act in the directions in which they cancel each other, and it is possible to reduce the elastic deformation of the movable table 4. Further, since the reference gauge 1 is only fitted to the fixed blocks 3a and 3b, the reference gauge can be easily replaced according to the application of the straightness meter.

Incidentally, a non-contact type detector can be used instead of the contact type detectors 5 and 6, and it is easily conceivable that an optical straight portion such as a laser beam is used as the reference straight portion instead of the reference surface 1a.

〔The invention's effect〕

As explained above, in the straightness meter of the present invention,
A guide rail having a longitudinal direction parallel to the reference straight part of the reference gauge is provided, and a movable base is slidably arranged on the guide rail, and an object to be measured with respect to the movable base is mounted on the movable base. The first displacement detector that detects the displacement of the linear portion and the second displacement detector that is fixed to the movable base and that detects the displacement of the movable base with respect to the reference straight portion are fixed together, and the first displacement The detection amount of the detector is corrected based on the detection amount of the second displacement detector, and the displacement of the linear portion of the object to be measured with respect to the reference straight portion is calculated. The effect can be obtained.

First, the movement error when the movable table does not move correctly on the guide rail can be detected by the second displacement detector, and the movement error is converted and corrected by correcting the detection amount of the first displacement detector. It is possible to remove the movement error due to the meandering motion of the platform. Therefore, the straightness accuracy of the reference straight portion may be the same as the accuracy of the straight portion that the conventional straightness uses as a reference, and the shape error of the guide rail or the sliding surface of the moving base does not pose any problem. Since the reference gauge is not affected by the weight of the moving table, it is possible to reduce the rigidity of the reference gauge, and even if a guide rail and a second displacement detector are added, the size of the entire straightness meter can be reduced. The increase can be small. Therefore, it is possible to improve the accuracy of straightness obtained by the straightness meter without increasing the accuracy of the components of the conventional straightness meter at all and after keeping the size to the minimum necessary increase. Is.

[Brief description of drawings]

1 to 4 are views showing an embodiment of the present invention. FIG. 1 is a front view of a straightness meter, FIG. 2 is a plan view of the straightness meter, and FIG. 3 is a straightness meter. 4 is a right side view of FIG. 4, and FIG. 4 is a sectional view taken along line AA of FIG. 1 ... Reference gauge, 1a ... Measurement reference plane, 2 ... Guide rail, 4 ... Movable table, 5,6 ... Lever displacement detector.

Claims (1)

(57) [Claims] 1. A reference gauge having a reference straight portion, a guide rail having a longitudinal direction in a direction parallel to the reference straight portion, and a movement movably provided on the guide rail parallel to the reference straight portion. A table, a first displacement detector fixed to the movable table to detect a displacement of a linear portion of the object to be measured with respect to the movable table, and a displacement detector fixed to the movable table to detect a displacement of the movable table with respect to the reference straight portion A second displacement detector and an arithmetic unit for correcting the detection amount of the first displacement detector based on the detection amount of the second displacement detector to calculate the displacement of the linear portion of the measured object with respect to the reference straight portion. A straightness meter characterized by comprising: